10.1.4 Tracepoint Action Lists

actions [num]

This command will prompt for a list of actions to be taken when the tracepoint is hit. If the tracepoint number num is not specified, this command sets the actions for the one that was most recently defined (so that you can define a tracepoint and then say actions without bothering about its number). You specify the actions themselves on the following lines, one action at a time, and terminate the actions list with a line containing just end. So far, the only defined actions are collect and while-stepping.

To remove all actions from a tracepoint, type ‘actions num’ and follow it immediately with ‘end’.

(No value for GDBP) collect data // collect some data (No value for GDBP) while-stepping 5 // single-step 5 times, collect data (No value for GDBP) end // signals the end of actions.

In the following example, the action list begins with collect commands indicating the things to be collected when the tracepoint is hit. Then, in order to single-step and collect additional data following the tracepoint, a while-stepping command is used, followed by the list of things to be collected while stepping. The while-stepping command is terminated by its own separate end command. Lastly, the action list is terminated by an end command.

(No value for GDBP) trace foo (No value for GDBP) actions Enter actions for tracepoint 1, one per line: > collect bar,baz > collect $regs > while-stepping 12 > collect $fp, $sp > end end

collect expr1, expr2, …

Collect values of the given expressions when the tracepoint is hit. This command accepts a comma-separated list of any valid expressions. In addition to global, static, or local variables, the following special arguments are supported:

$regs

collect all registers

$args

collect all function arguments

$locals

collect all local variables.

You can give several consecutive collect commands, each one with a single argument, or one collect command with several arguments separated by commas: the effect is the same.

The command info scope (see section info scope) is particularly useful for figuring out what data to collect.

while-stepping n

Perform n single-step traces after the tracepoint, collecting new data at each step. The while-stepping command is followed by the list of what to collect while stepping (followed by its own end command):

> while-stepping 12 > collect $regs, myglobal > end >

You may abbreviate while-stepping as ws or stepping.